Hydrogels of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) are used in a variety of biomedical and pharmaceutical applications including tissue scaffolds, cartilage repair, and drug delivery. Various methods have been proposed for making such hydrogels. For example, some methods for hydrogel preparation from poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) are based on the incorporation of vinyl functionalities into macromers with consequent photopolymerization that requires the use of photoinitiators and a UV source. In other cases, PVA is end-capped with thiol groups and cross-linked with methacryloyl-substituted PVA. However, many of these systems require the use of initiators, (which may be toxic), UV radiation, organic solvents, and temperatures outside of those tolerable in physiological conditions.
Accordingly, room still remains for improvement in systems that can be injected and form hydrogels in situ under physiological conditions without toxic initiators, UV radiation, organic solvents or elevated temperatures. In addition, hydrogel systems that are degradable and biocompatible are desired that form degradation products that pass through the kidneys. Furthermore, it is desirable to provide a polymer system that is capable of both crosslinking for the purpose of hydrogel formation and mucoadhesion.